The present invention relates to a method for characterizing the compositional distribution at the internal surface of a contact hole in the direction of its depth after the contact hole is formed to contribute to establishing a contact hole formation process in the method for manufacturing semiconductor integrated circuits.
With higher integration in large-scale semiconductor integrated circuit (hereafter referred to as LSI) devices increasingly called for in recent years, the number of circuit elements is rising. This has resulted in an increase in the number of contact holes required for forming wiring, and the diameter of these contact holes is steadily being reduced. Because of this, formation of contact holes is becoming ever more difficult. Contact holes are formed through etching. On the internal surface of a contact hole formed through etching, a deposited film is formed with an etching gas or the like. This deposited film is basically constituted of the accumulated residue from the etching process. In order to establish a method for forming contact holes, it is necessary to optimize the etching process by examining the compositional distribution of the deposited film.
A method in the prior art for determining the compositional distribution at the internal surface of a hole is disclosed in a publication entitled "Electronics Information Communication Society Technical Report," Vol. 93, No.369, pp.47-52. In the method disclosed in this publication, the internal surface of a through hole is exposed by cutting open a multilayer wiring test piece. Then, by employing Auger electron spectroscopy, the deposited film formed at the internal surface of the through hole is analyzed.
However, no method for analyzing the compositional distribution at the internal surface of a contact hole with a diameter in the deep submicron range, or several tens of nanometers (nm), and a depth of 1 micrometer or more has been disclosed to date. Thus, optimization of the etching process for contact holes has not been achieved, and it has been difficult to form contact holes with an aspect ratio of, for instance, 20:1.